Communications through wireless communication links has become quite common in recent years due to such considerations as improved radio technologies and modulation techniques, reduced cost of infrastructure deployment, and support for station mobility. However, the providing of wireless communications is not without challenges and tradeoffs. For example, wireless communication links are often susceptible to interference (both from other stations within the communication network and sources external to the communication network), provide a limited service area, and often experience reduced capacity in accommodating station, mobility.
Many wireless communication systems, for example, have utilized omni-directional antenna patterns or antenna beams in order to provide wireless communication links throughout a service area. However, such omni-directional antenna patterns are highly susceptible to interference and typically introduce interfering signals to other systems. Moreover, the area serviced by such omni-directional antenna patterns is often relatively small in radius due to the gain available from antenna systems providing omni-directional antenna patterns. Capacity issues, such as resulting from the aforementioned interference, and limitations on the size of the service area often necessitate increased numbers of base stations, and thus increased costs and complexity, in an omni-directional system configurations.
Wireless communication systems have, more recently, adopted directional antenna beam configurations. Such directional antenna beam configurations may typically be used to decrease interference and to potentially extend the range of a base station. However, directional antenna beam configurations are often highly complex and costly, both in initial infrastructure cost as well as communication and processing costs.
For example, directional antenna configurations often require a radio for use with each directional active antenna beam formed, thus often necessitating a relatively large number of radios to provide communications within a large service area. Moreover, in order to form the appropriate directional beams the base station must have very accurate channel state information, thus utilizing appreciable overhead for channel state information feedback from the stations (e.g., multiple subscriber stations operating within the service area). Subscriber stations must often be provided with sophisticated algorithms and circuitry for collecting the channel state information necessary for implementing proper directional antenna patterns. The time required for a station to collect and communicate the channel state information to a base station can result in the channel state information available at the base station being relatively old. In a highly mobile environment or a fast fading environment such outdated information can be insufficient for proper control of directional antenna patterns. Assuming appropriate channel state information is available at a base station, substantial processing power is typically required to analyze the channel state information and to derive the beam forming parameters to provide a directional antenna pattern optimized for the channel state. Where multiple stations are provided communications simultaneously, the overhead and processing requirements can be daunting.
Accordingly, the various wireless communication systems available today have not been found by the inventors of the present invention to provide an ideal mix of service area coverage, system capacity, and low cost.